Subject:
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Re: Hangin' around
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Newsgroups:
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lugnet.cad
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Date:
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Wed, 16 Aug 2006 09:55:57 GMT
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Viewed:
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1715 times
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In lugnet.cad, Travis Cobbs wrote:
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In lugnet.cad, Timothy Gould wrote:
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On the topic of jpegs, if you convert them at high enough quality (I use
-quality 90% setting from IM convert) I think they can actually look better
than lossless images because the compression rounds off some of the harsher
lines in the renders. I switched to using jpegs for all my wallpapers quite
a while ago and keep the png format for any further manipulation.
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In my experience JPEG versions of computer-generated pictures only really
look good when you turn off color sub-sampling during the JPEG compression.
Many (most?) programs that allow you to create JPEG images don’t support this
option. It also doesn’t seem to have a consistent terminology. In Irfanview,
check the “Disable color subsampling” option in the JPEG save options box.
In ACDSee, I think it’s something like 1x1 sampling vs 2x2 sampling.
One of the below images used color subsampling. The other didn’t. Can you
tell which is which? (Note that I created PNG crops of the original JPEG
images.)
Notice in particular the red edge lines, and how much more crisp they are in
one of the images. Note that both images were saved with quality set to 90%.
The subsampled original image was 45KB. The other was 57KB. The original
PNG was 50KB, but the full original had a lot of white background, and PNG
does a much better job on this than JPEG.
One thing to note is that even though many programs don’t support generating
JPEG files like this, all JPEG viewers should support displaying them.
--Travis
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Hi Travis,
I didn’t realise that you could switch off parts of jpeg compression. Very handy
to know. I didn’t quite spell it out in my previous post but I actually meant
for raytraced images rather than general renders. For edge-lined renders like
ldglite or ldview generate I wouldn’t use jpeg because of what the compressed
Fourier transform does to the edges. However since a raytrace is meant to be a
simulation of the real world and jpeg is designed for real world images I find
that it works fine.
Tim
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Message is in Reply To:
 | | Re: Hangin' around
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| (...) In my experience JPEG versions of computer-generated pictures only really look good when you turn off color sub-sampling during the JPEG compression. Many (most?) programs that allow you to create JPEG images don't support this option. It also (...) (18 years ago, 15-Aug-06, to lugnet.cad, FTX)
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